In general, a rough terrain crane includes a carrier device that is capable of four-wheel driving and four-wheel steering, and exhibits excellent small-radius turning performance and rough terrain traveling performance. The rough terrain crane includes a single driver seat or operating unit, has special performance that enables an operator on the driver seat to drive a vehicle and to perform operation of a crane mounted on the vehicle. The rough terrain crane is manufactured based on a compact design so as to exhibit such special performance. Therefore, an entire vehicle body is designed to be short, an engine (in general, a diesel engine) is disposed on a rear side of the vehicle body, and an elevating step or an exhaust emission control device, which will be described below, is disposed around a fender (for example, see Patent Document 1).
The exhaust emission of diesel engines contains particulate matter (hereinafter, referred to as “PM”), nitride oxide (hereinafter, referred to as “NOx”), or the like. The exhaust emission control device prevents the matter from being released into the air and prevents the air from being polluted. The exhaust emission control device includes, as the constituent elements, a diesel particulate filter (hereinafter, referred to as a “DPF”) for collecting the PM, a diesel oxidation catalyst (hereinafter referred to as “DOC”) for removing the NOx, a decomposition reactor tube (hereinafter referred to as “DRT”), and a selective catalytic reduction (hereinafter referred to as “SCR”). By combining the constituent elements, a desired exhaust emission control device is constituted (for example, see Patent Document 1).
However, in a large rough terrain crane, a front axle or a rear axle has a multi-axle structure, and a structure with a premise of attaching and detaching an outrigger and a boom to and from a vehicle-body frame is employed in some cases. The main reason for the front axle or the rear axle to have the multi-axis structure is to reduce the entirety of axle load to a certain load or lower. In addition, the reason for the structure with the premise of attaching and detaching the outrigger and the boom to and from the vehicle-body frame is employed is to be in accordance with the legislation of a country or a region where the large rough terrain crane is used. In other words, in some countries or regions, strict weight limit (axle load limit) is imposed on a vehicle traveling on a public road. Therefore, when the large rough terrain crane runs on a public road, the vehicle body, the outrigger, and the boom must be individually transported on a trailer in some cases.
In the large terrain crane employing the premise of attaching and detaching the outrigger or the boom, layout design of accessory machinery such as the exhaust emission control device and the elevating step has a low degree of freedom in utilizing a space around the fender. In other words, since the large rough terrain crane lifts a load having a heavy weight, a counterweight, or the like, in addition to the boom and the outrigger, has a large size; however, in a circumstance, a vehicle body (particularly, a vehicle width) is not allowed to increase in size so as to maintain a compact size as a characteristic of the rough terrain crane, and thus a space, in which the exhaust emission control device or the like is to be disposed, is reduced.